“It’s clear to me he understands the fork in the road America is facing,” Ryan said, adding, “I also think he has the best chance of winning and defeating Barack Obama in the fall.”

Ryan, who chairs the House Budget Committee, is from Wisconsin, where Republican voters will vote in their primary next week.

The Milwaukee Journal-Sentinel reported that Ryan would join Romney on the campaign trail in Wisconsin before the primary.

The endorsement caps a week of nods from big name Republicans, young and old. On Thursday, former President George H.W. Bush made an earlier endorsement official. And earlier this week, Florida Sen. Marco Rubio endorsed Romney.

Both Ryan and Rubio are on most political watcher’s list of potential vice presidential picks for Romney, but Ryan said that didn’t factor into his endorsement.

“No that’s ridiculous we’ve never discussed that at all,” he told the Fox News anchor. “My focus has been on the budget, I haven’t given any of that serious thought.”